JPH09142916A - Spinel-containing refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a spinel-containing refractory having excellent corrosion resistance and excellent spalling resistance by incorporating a prescribed quantity of a MgO-enriched electromelted spinel containing MgO and Al2 O3 in a specific ratio. SOLUTION: The MgO-enriched electromelted spinel constituted so as to cover the whole or a part of the surface of a magnesia particle containing 55-85% MgO and 45-15% Al2 O3 and forming a solid solution of Al2 O3 on the surface with a spinel composition is prepared. Next, a raw material containing 5-100% MgO-enriched electromelted spinel and the balance a basic raw material (e.g. electromelted magnesia) with alumina fine powder is prepared, molded and fired to produce the spinel-containing refractory. As a result, the deterioration of the corrosion resistance is prevented by increasing the content of MgO and at the same time, the spalling resistance is improved by uniformly dispersing the spinel in spite of small content of Al2 O3 . The resultant spinel-containing refractory is suitable for the lining of a vessel for molten metal refining.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a spinel-containing refractory used for lining a vessel for refining molten metal, and more particularly to a spinel-containing refractory having excellent spalling resistance without lowering corrosion resistance.

[0002]

2. Description of the Related Art Conventionally, as a refractory material containing spinel, magnesia / spinel bricks, which are a combination of magnesia and spinel, have been used in cement rotary kilns, stopper sleeves, etc., and dolomite bricks and magcro bricks are mainly used. Recently, some magnesia spinel bricks have also started to be used in VOD pots.

Damages of this VOD pot include damage due to reaction with slag components, damage due to structural spalling due to slag infiltration, and damage due to thermal spalling. In order to reduce these damages. As a means to enhance the heat-resistant spalling resistance of magnesia bricks with excellent corrosion resistance, magnesia has a theoretical composition spinel (MgO
28% and Al ₂ O ₃ 72%) were added to the magnesia spinel bricks.

[0004]

By the way, this magnesia spinel brick has high corrosion resistance as a refractory material and high spalling resistance, but it is possible to impart higher corrosion resistance and spalling resistance. It has been demanded.

However, as a result of repeated research,
The more the shear resistance of shear spinel bricks, the more magnesia
However, if magnesia is increased, the spalling resistance will increase.
It turned out to drop. Also, magnesia spinel
Corrosion resistance of bricks Al of bricks _TwoO_ThreeAffected by the content,
Al_TwoO_ThreeIt can be seen that the higher the content, the worse the corrosion resistance.
won.

That is, if the magnesia of magnesia-spinel brick is increased to increase the corrosion resistance, the spalling resistance decreases, and if the spinel is increased to increase the spalling resistance, the corrosion resistance decreases. There is a problem.

The inventors have discovered that the use of magnesia-rich electrofused spinel can enhance the corrosion resistance without lowering the spalling resistance, and have completed the present invention.

[0008] That is, an object of the present invention is to provide a spinel-containing refractory which can enhance corrosion resistance without lowering spalling resistance.

[0009]

In order to achieve the above object, the spinel-containing refractory material according to the present invention comprises MgO55-
85%, Al ₂ O ₃ 15 to 45% MgO rich electrofused spinel is contained at 5 to 100% or more.

The MgO rich electrode used in the present invention
Molten spinel is Al_TwoO_ThreeSolid solution of magnesia (Mg
O) All or part of the surface of the particles is covered with the spinel composition.
The composition is MgO with emphasis on corrosion resistance.
55-85%, Al_TwoO_Three15-45% is preferred
Good. More preferably MgO 65-85%, Al_TwoO
_ThreeIt is 15 to 35%.

When the content of Al ₂ O ₃ is less than 15, that is, when the content of MgO exceeds 85%, it is advantageous for enhancing the corrosion resistance, but the formation of the spinel layer surrounding the magnesia particles is generated. It is difficult because it is difficult. Further, when the content of Al ₂ O ₃ exceeds 45%, that is, when the content of MgO is less than 55%, corrosion resistance may be deteriorated, which is not preferable.

Since this MgO-rich electrofused spinel has a smaller content of Al ₂ O ₃ than the theoretical composition spinel,
If the amount is the same, the corrosion resistance is less likely to be impaired, which is advantageous in enhancing the corrosion resistance.

Further, as compared with the case of using the theoretical composition spinel, the spinel is easily dispersed uniformly even if the amount of Al ₂ O ₃ used is small, and the spalling resistance, especially the heat-resistant spalling resistance can be enhanced.

In the present invention, the amount of the MgO-rich electrofused spinel used is preferably 5 to 100%. When the amount of the MgO-rich electrofused spinel used is less than 5%, the addition of the spinel can improve the resistance. It is not preferable because the effect of improving the spalling property cannot be sufficiently obtained.

When the amount of this MgO-rich electrofused spinel used is 5% or more and less than 100%, the balance is a basic raw material for not lowering the corrosion resistance and alumina for improving the sinterability of the refractory. It is preferably composed of fine powder, and examples of this basic raw material include electrofused magnesia, sintered magnesia, dolomite clinker, electrofused spinel, and sintered spinel. This spinel may have a theoretical composition or a MgO rich composition. The amount of fine alumina powder added is preferably 0.5 to 5%, and 0.5%
If it is less than 5%, the effect of enhancing the sinterability becomes insufficient, and if it exceeds 5%, the corrosion resistance may decrease, which is not preferable. The particle size of the alumina fine powder is preferably 45 μm or less in order to improve dispersibility,
More preferably, the thickness is 20 μm or less.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in Table 1 below, electrofused magnesia 8 to 93%, MgO rich electrofused spinel (M
gO / Al ₂ O ₃ = 70/30) 5 to 90% and alumina fine powder 2% at the compounding ratio (%) shown in each column of Example 1 to Example 6 in Table 1 and kneading under the same conditions. After molding, the bricks were fired at 1800 ° C. to obtain bricks according to Examples 1 to 6.

Similarly, as shown in Table 1, electrofused magnesia 68 to 95%, electrofused spinel (theoretical composition) 0 to 3
0% and 2% of alumina fine powder were blended at the blending ratio (%) shown in each column of Comparative Example 1 to Comparative Example 4 in Table 1, kneaded under the same conditions as in Examples 1 to 6 and molded, 1800 ° C
Baking was performed to obtain bricks according to Comparative Examples 1 to 4.

The particle size composition of the constituent raw materials in each example and each comparative example is the same.

[0019]

[Table 1]

These Examples 1 to 6 and Comparative Examples 1 to 4 were lined in a high frequency furnace according to the high frequency furnace lining method, and steel and synthetic slag (CaO) were used as an erosion agent.
50%, Al ₂ O ₃ 40%, SiO ₂ 10%) were melted therein and held at 1750 ° C. for 4 hours, and the corrosion resistance was evaluated by the amount of erosion loss of each brick. I got the result.

In FIG. 1, the vertical axis represents the melting loss index, the horizontal axis represents the Al ₂ O ₃ content (%) in the entire brick composition, the ● symbol represents the example, and the ○ symbol represents the comparative example. Alternatively, the number attached to the circle indicates the number of the example or comparative example.

From Table 1 and FIG. 1, the melt loss increases as the amount of Al ₂ O ₃ used increases in each of the examples using MgO rich spinel and the comparative examples using theoretical composition spinel. Although there is a tendency, when the amount of Al ₂ O ₃ used is the same, the amount of erosion loss is smaller and the corrosion resistance is superior in each of the examples using MgO rich spinel as compared with the comparative example using the theoretical composition spinel. I understand that.

Next, 30 mm × 50 mm × 250 mm rectangular parallelepiped Examples 1 to 6 and Comparative Examples 1 to 4 were each immersed in hot metal at 1550 ° C. for 90 seconds, then taken out and allowed to cool for 20 minutes. The above operation was repeated, and the spalling resistance was evaluated by the number of repetitions until the surface was peeled off in Examples 1 to 6 and Comparative Examples 1 to 4 and shown in Table 1 and FIG. I got the result.

In FIG. 2, the vertical axis represents the number of times until peeling, the horizontal axis represents the Al ₂ O ₃ content (%) in the entire brick composition, the ● mark represents an example, and the ○ mark represents a comparative example. ,
The numbers attached to the ● or ○ marks indicate the numbers of the examples or comparative examples.

From Table 1 and FIG. 2, if the amount of Al ₂ O ₃ used is the same, each of the examples using MgO-rich spinel has a larger number of repetitions than the comparative example using the theoretical composition spinel. It can be seen that the heat-resistant spalling property is excellent.

In short, if the amount of Al ₂ O ₃ used is the same, MgO is higher than that of the comparative example using the theoretical composition spinel.
Since each example using the rich spinel is also superior in corrosion resistance and heat-resistant spalling resistance, a spinel-containing refractory having excellent spalling resistance is obtained without lowering corrosion resistance. .

[0027]

As described above, the spinel-containing refractory material of the present invention contains MgO 55-85%, Al ₂ O ₃ 15
Since 45% to 45% of MgO-rich electrofused spinel was contained, it is possible to prevent the deterioration of corrosion resistance by increasing the mixing ratio of MgO, and at the same time, even though the mixing amount of Al ₂ O ₃ is small, the spinel Can be uniformly dispersed to improve spalling resistance.

[Brief description of the drawings]

FIG. 1 is a corrosion resistance characteristic diagram showing a comparison of corrosion resistance between an example of the present invention and a comparative example.

FIG. 2 is a heat-resistant spalling property chart showing the heat-resistant spalling properties of Examples and Comparative Examples of the present invention in comparison.

Claims (2)

[Claims] 1. MgO 55-85%, Al ₂ O ₃ 15-
A spinel-containing refractory material containing 5 to 100% of 45% MgO-rich electrofused spinel. 2. The content of MgO-rich electrofused spinel is 5
% Or more and less than 100%, and the balance is a basic raw material and alumina fine powder, The spinel-containing refractory material according to claim 1.